1. Field of the Invention
The present invention generally relates to the art of mass spectrometry. Particularly, it is concerned with a sample holding element for use in a mass spectrometer capable of introducing samples or solid specimens containing substances which had hitherto been considered to be very difficult to introduce into a vacuum chamber (ionization chamber) of a mass spectrometer. Such substances include those having excessively large or small volatility and those which are liable to sublimation. On the contrary, substances which are hard to sublime are also very difficult to be introduced. Furthermore the present invention relates to a sample holding element which enables the qualitative identification as well as quantitative determination of the respective compounds included in a mixture sample which is difficult to separate into the respective components at the preceding step.
2. Description of the Prior Art
Of various modes of sample introduction by means of conventional probes in the field of mass spectrometry, an indirect thermal introducing method wherein a reservoir for heated gas of large capacity is connected to an ion source, has hitherto been customarily employed. Disadvantages inherent to this method include a residual effect from the previously measured material which affects the sample to be determined thereafter and is quite frequent with ordinary organic compounds. Moreover a high probability of deteriorating or decomposing the compound during its long travel through an elongated pipeline kept at high temperature, has been confining the application of mass spectrometry to some limited species of substances over the years.
Under the stated circumstances, the so-called direct introduction method has recently been developed and has become prevalent. One conventional sample probe for use in this method includes a rod having a simple pot-like cavity for accomodating a sample or specimen at its tip. Should a liquid sample of especially high volatility have to be handled, an undesirable instant vaporization must inevitably be entailed, which must be suppressed or at least delayed by stuffing the cavity with a material such as asbestos despite the fact that such a material may be considered as being detrimental to the operators due to its suspected strong carcinogenicity.
Even when exercising a deliberate manipulation, the method of handling this probe, however, might lead to an inaccurate quantitative value of determination due to a possible insufficient ionization of the sample. The stuffing material may sometimes disperse so as to contaminate or pollute the environment around the equipment during the evacuating operation of the ion source after the specimen has been introduced. If the manual operation entails the contamination of the stuffing material, an increase in the noise level of the signal might be inevitable.
Recently, the scope of the sample which may be identified and determined by mass spectrometry has been extended to a great extent by the employment of the so-called "GC-MS" system which is a combination of a mass spectrometer with a separating means by gas chromatography. Even if the high cost of the GC-MS apparatus might be tolerated, this system has a serious disadvantage in that it is not suited for handling an unstable substance which may be extensively decomposed by heat applied thereto during the process of gas chromatography. In such cases, the sample might frequently require an additional operation of chemical modification to avoid such thermal decomposition prior to the gas chromatography by, for instance, silylation or acylation.